Structure and function relationship of floral scent carboxyl methyltransferases
Final Report Abstract
We succesfully isolated 12 SA/BA carboxyl methyltransferase genes from related Nicotiana species. These SAMT and BSMT genes allowed us to discern levels of enzyme divergence resulting from gene duplication in addition to species divergence. The phylogenetic analysis showed that the genes evolved in separate clades. A new BSMT2 branched was established and after duplication the BSMT enzymes evolved higher preference for the substrate BA than SA, A novel enzyme displays a high activity with nicotinic acid and the synthesis of methyl antranilate via BSMT2 contrasts with the biosynthetic route previously proposed. We further used a combined statistical and experimental (biochemical) approach to test the recently proposed innovation, amplification and divergence (IAD) model of protein evolution. Ancestral functional promiscuity evolved to become the primary activity of daughter enzyme after gene duplication and coincides with positive selection. These results were supported by the mutagenesis studies. In one case, the occurrence of an evolutionary reversal was documented. The positive selection resulted in substrate discrimination by changes the catalytic efficiencies. Together these data support the IAD model.
Publications
- Localization of methyl benzoate and methyl salicylate synthesis and emission in Stephanotis floribunda and Nicotiana suaveolens flowers. Plant Biology 8: 615-626, 2006
Rohrbeck D., Buss D., Effmert U., Piechulla B.
- Localization of the synthesis and emission of scent compounds within the flower. In: Floral Scents (eds. Dudareva N., Pichersky E.), CRC Press Taylor and Francis Group, London, p. 105-124, 2006
Effmert U., Buss D., Rohrbeck D., Piechulla B.
- Regulation of simultaneous synthesis of floral scent terpenoids by the 1,8-cineole synthase of Nicotiana suaveolens. Plant Molecular Biology 65: 107-124, 2007
Roeder S., Hartmann AM., Effmert U., Piechulla B.
- Influence of green leaf herbivory of Manduca sexta on floral volatile production and emission of Nicotiana suaveolens. Plant Physiology 146: 1996-2007, 2008
Effmert U., Dinse C., Piechulla B.
- SAM levels, gene expression of SAM synthase, methionine synthase and ACC oxidase, and ethylene emission from N. suaveolens flowers. Plant Molecular Biology 70: 535-546, 2009
Roeder S., Dreschler K., Piechulla B.
- Biosynthesis and regulation of flower scent. In: Plant Developmental Biology and Biotechnological Perspectives (Eds: Eng-Chong Pua, Mike Davey) Springer Heidelberg, pp 189-205, 2010
Piechulla B., Effmert U.
- Enzymatic, expression and structural divergences among carboxyl O-methyltransferases after gene duplication and speciation in Nicotiana. Plant Molecular Biology, 72:311-330,2010
Hippauf F., Michalsky E., Huang R., Preissner R., Barkman TJ., Piechulla B.
